I have a text area at my site.This site has a menu bar in the left and in the centre is that text area.In some resolutions of the screen there is a horizontal scrollbar for the text.Is there a way with css to "disappear" this scrollbar ?

Yes as said above you should not rely on having the text small just so that you don't get a scrollbar.

The size of text is unlikely to be the issue that a scrollbar appears anyway and the culprit is usually that when the vertical scrollbar kicks in it steals some real estate from the fixed width div and thus causes the horizontal scrollbar as well.

You should nest an inner div inside the overflow div and make it about 20px approx smaller than the parent to allow a scrollbar to pop in and out easily.

However, I didn't notice a horizontal scrollbar on that layout even when zooming text right up.